Diabetogenic Mine Tailings: Mechanistic Link Between Arsenic, NRF2, Autophagy, and Diabetes

总结（项目1：Donna Zhang） 土壤和水被含金属的有害物质污染，特别是在矿区附近 尾矿和冶炼厂，导致附近社区长期接触有毒金属混合物， 严重的健康问题。根据有毒物质疾病登记局的数据，该数字 在这些地点与尾矿相关的一种污染物是有毒的准金属砷（As）。流行病学 研究表明，无论是通过饮用水， 或食物，糖尿病的发病率增加。因此，接触含砷尾矿， 结果吸入或摄入砷，可能是一个显着的贡献者，以增加疾病的风险，在暴露 社区.重要的是，尽管已知的健康影响的严重性，分子机制， 含砷尾矿增强糖尿病表型尚未阐明。此前我们 报道说，低的，环境相关剂量的砷阻断自噬，一个关键的细胞降解 维持蛋白质稳态的关键途径。此外，我们已经表明，自噬功能障碍的结果， 关键的抗氧化转录因子NRF 2的长期激活。通常维持在低水平 通过KEAP 1介导的泛素化和26 S蛋白酶体的降解，NRF 2在26 S蛋白酶体中上调。 通过KEAP 1的氧化修饰（KEAP 1-C151依赖性，典型）或 Keap 1在As诱导的自噬功能障碍期间进入自噬体（p62依赖性，非经典）。而 通过Keap 1-C151依赖的经典机制控制Nrf 2激活是保护性的，延长 砷暴露期间NRF 2的p62依赖性非经典激活导致细胞功能障碍和组织损伤 损伤，表明NRF 2的“黑暗面”。我们假设，含砷尾矿促进 糖尿病通过p62依赖性，Nrf 2的长期激活。这一假设得到了我们的支持。 初步数据表明，暴露于As的野生型（WT）小鼠显示葡萄糖耐量受损， 增强的胰岛素抵抗，这在Nrf 2-/-、p62-/-或Nrf 2-/-p62-/-小鼠中未观察到。我们最近的RNAseq 从暴露于砷20周的小鼠肝脏中产生的数据也显示了在肝脏中的显著变化。 参与葡萄糖、胰岛素、胆固醇和脂质代谢的基因的表达。在这个应用程序中，我们将 通过以下方法检验我们的假设：1）描述慢性糖尿病的时间和剂量依赖性糖尿病发生潜力， WT小鼠暴露于饮用水或尾矿As颗粒（PM10）中的As（目的1）; 2）确定 NRF 2激活延长在糖尿病相关细胞中驱动As诱导的代谢重编程中的作用 细胞系（目的2）; 3）在体内证实As和延长NRF 2诱导的重要分子改变 促进糖尿病的活性（目的3）。对砷介导的改变的机械理解， 糖尿病将被证明在诊断、预防和治疗策略的制定方面极其有价值 暴露于含砷尾矿的人群和有砷暴露风险的人群。

SUMMARY (Project 1: Donna Zhang) Contamination of soil and water by metal-containing hazardous substances, particularly at sites near mine tailings and smelters, has led to chronic exposure of nearby communities to toxic metal mixtures, posing a serious health problem. Based on data from the Agency for Toxic Substances Disease Registry, the number one contaminant associated with mine tailings at these sites is the toxic metalloid arsenic (As). Epidemiological studies have demonstrated a positive correlation between chronic As exposure, either through drinking water or food, with an increased incidence of diabetes. Thus, exposure to As-containing mine tailings, which could result in inhalation or ingestion of As, may be a significant contributor to enhanced risk of disease in exposed communities. Importantly, despite the known severity of the health effects, the molecular mechanisms by which As-containing mine tailings enhance diabetic phenotypes have not yet been elucidated. Previously, we reported that low, environmentally relevant doses of arsenic block autophagy, a key cellular degradation pathway critical to maintaining proteostasis. Furthermore, we have shown that autophagic dysfunction results in prolonged activation of the key antioxidant transcription factor NRF2. Normally maintained at low levels through KEAP1-mediated ubiquitination and degradation by the 26S proteasome, NRF2 is upregulated at the protein level via oxidative modification of KEAP1 (KEAP1-C151 dependent, canonical) or sequestration of Keap1 into autophagosomes during As-induced autophagy dysfunction (p62-dependent, non-canonical). While controlled Nrf2 activation through the Keap1-C151 dependent canonical mechanism is protective, prolonged p62-dependent non-canonical activation of NRF2 during As exposure causes cellular dysfunction and tissue damage, indicative of a “dark side” to NRF2. We hypothesize that As-containing mine tailings promote diabetes through p62-dependent, prolonged activation of Nrf2. This hypothesis is supported by our preliminary data indicating that wild type (WT) mice exposed to As showed impaired glucose tolerance and enhanced insulin resistance, which was not observed in Nrf2-/-, p62-/-, or Nrf2-/-p62-/- mice. Our recent RNAseq data generated from the liver of mice exposed to As for 20 weeks also showed significant changes in the expression of genes involved in glucose, insulin, cholesterol, and lipid metabolism. In this application, we will test our hypothesis by: 1) characterizing the time and dose-dependent diabetogenic potential of chronic exposure to As in drinking water or mine tailing As-particles (PM10) in WT mice (Aim 1); 2) determining the role of prolonged NRF2 activation in driving As-induced metabolic reprogramming in diabetes-relevant cell lines (Aim 2); and 3) in vivo confirmation of important molecular alterations induced by As and prolonged NRF2 activity in promoting diabetes (Aim 3). A mechanistic understanding of arsenic-mediated alterations that lead to diabetes will prove extremely valuable in the generation of diagnostic, preventive, and therapeutic strategies for populations exposed to As-containing mine tailings and populations at risk of arsenic exposure.